Managed to get an 84. The strategy of this game seems simple, just let a 2 competence person plot against you forever and kill the other 2 as soon as they start wavering; if it's a 1 endurance character you kill them as soon as they spawn.
It's definitely possible to go infinite. I've attached my 243 score. This one I ended because I got distracted. The only real danger is the endurance: 1s which require a relatively fast kill time.